ASASSN-16ex: Discovery of A Probable Supernova in SDSS J171023.63+262350.3

ATel #9020; S. Kiyota (Variable Star Observers League in Japan), J. Brimacombe (Coral Towers Observatory), J. S. Brown, K. Z. Stanek, T. W.-S. Holoien, C. S. Kochanek, D. Godoy-Rivera, U. Basu (Ohio State), B. J. Shappee (Hubble Fellow, Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), D. Bersier (LJMU), Subo Dong, Ping Chen (KIAA-PKU)
on 4 May 2016; 01:57 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Jonathan Brown (brown@astronomy.ohio-state.edu)

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During the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin"), using data from the quadruple 14-cm "Brutus" telescope in Haleakala, Hawaii, we discovered a new transient source, most likely a supernova, in the galaxy SDSS J171023.63+262350.3.

ASASSN-16ex (AT 2016ccj) was discovered in images obtained on UT 2016-05-03.43 at V~17.5 mag. We also detect the object in images taken on UT 2016-04-30.43 (V~18.0). We do not detect (V>18.1) the object in images taken on UT 2016-04-29.51 and before. An image obtained on 2016-05-03 by S. Kiyota confirms the discovery of the transient. This figure shows the archival SDSS g-band image of the host (left) and the S. Kiyota confirmation image (right). The red circle has a radius of 5" and is centered on the position of the transient in the S. Kiyota image.

The position of ASASSN-16ex is approximately 1.9" South and 3.8" East from the center of the galaxy SDSS J171023.63+262350.3 (no redshift information available from NED). Properties of the new source and photometry are summarized in the tables below:

 
Object       RA (J2000)     DEC (J2000)      Disc. UT Date   Disc. V mag  Approx. Abs. Mag   Offset from Host (") 
ASASSN-16ex  17:10:23.919   +26:23:47.89     2016-05-03.43      17.5            N/A               4.25 

 
Obs. UT Date         V mag 
2016-04-29.51        >18.1 
2016-04-30.43         18.0 
2016-05-03.43         17.5 

Follow-up observations are encouraged.

While we are participating in the TNS system to minimize potential confusion, ASAS-SN will continue using ASASSN-16xx transient names as our primary nomenclature (including supernovae, but also other classes of transients), and we encourage others to do the same. We prefer merging the names as ASASSN-16xx (AT2016xyz) to preserve, rather than anonymize, the origin of the transient.

We thank LCOGT and its staff for their continued support of ASAS-SN. ASAS-SN is supported by NSF grant AST-1515927, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, the Mt. Cuba Astronomical Foundation, George Skestos, and the Robert Martin Ayers Sciences Fund. For more information about the ASAS-SN project, see the ASAS-SN Homepage and the list of all ASAS-SN transients.